In the past, a variety of formed plastic sheets have been used as foundational and drainage members under sods, plantings and gravels, as well as roofs and decks of concrete. These plastic sheets commonly comprise a series of raised dimples that are round, square, conical or rectangular in shape. These dimples provide structural integrity to the mat. Drainage channels are often separately disposed between the dimples to provide for water run-off. The mat is usually overlaid with a screen mesh of polypropylene or one of a variety of non-woven fabrics that allow some permeability and additional support.
The drainage channels draw off most of the water from these mats, but the dimples themselves collect water for which there is no outlet. The amount of dimple-retained water is small compared to that involved in the drainage channel run-off, but this small amount of water nevertheless tends to freeze or thaw, depending on the weather. Freezing and thawing cause expansion and contraction stresses in the foundation. This dimple-retained water is also a breeding place for fungi, bacteria and odor-causing organisms. Eventually, this dimple-retained water will cause deterioration of the plastic dimples and, hence, undermine the mat foundation.
The present invention features a new drainage mat design that provides slots through or adjacent to the dimples. Connected to the main drainage channels, these slots act as drainage channels for the dimples. These added slots, therefore, provide a positive drainage that eliminates the dimple-retained water.
In addition, the prior-art mats have generally been designed for a maximum support of about 14,400 psf or approximately 100 psi. Unfortunately, this load capability is usually insufficient to accommodate heavy traffic, such as trucks and snow-removal equipment. Furthermore, these prior-art mats did not provide for the proper drainage necessary for the exterior installation of ceramic tile, marble, stone or other rigid material. If not properly supported, such additional materials can crack under a heavy load. Without the proper drainage, moisture can also accumulate in the load-bearing mortar and cause severe frost damage.
The current invention features a new, load-bearing design for a drainage mat that will support the aforementioned heavier loads, as well as eliminate the need for additional overlays of strengthening mesh or fabric.
The added, load-bearing capability of the inventive mat allows for an overlay of a two-inch concrete topping, which will increase the overall composite's capability for support. The composite will then be able to support extremely heavy traffic loads, such as snow-clearing and maintenance equipment. The unique design of this invention reduces the overall thickness of the conventional four-inch concrete or mortar support for ceramic and marble, thereby reducing dead load by 50% and/or by 30 psf.